In general, a buckle has a configuration in which two facing members are coupled to each other and fixed, and has been used in various technology fields. Among them, in the case of a vehicle, a buckle is mainly used for a seat belt provided in a seat. In the case of a buckle used for a seat belt, it is necessary to consider unexpected release of the buckle caused by a vehicle collision impact as well as the convenience for the driver.
That is, in a normal use, easy locking and release of the buckle is important so that a driver can easily lock or release the seat belt. However, in the case of a vehicle collision, it is necessary to prevent the buckle from being released by an unexpected external impact.